**Nomenclature**

*Current Topics in Biochemical Engineering*

absorption on the NIR. As for the GNPs, they exhibit their characteristic absorption between 520 and 530 nm [29]. However, on the seeded silica particles, the slight shift to the NIR is noticeable. While on the GNS, the peak not only shifted to the NIR, but it kept a high absorbance all the way to 1100 nm. This range is part of the optical window of the human body [5]. The absorbance of the GNSs is due to the SPR that creates an electric field on the surface increasing the absorption of these wavelengths. SPR happens when metal nanoparticles are irradiated with a wavelength

*Thermography images of the GNS taken (a) before and (b) after being irradiated with 840 nm wavelength* 

To verify the absorbance of the GNS, they were irradiated with an 840 nm laser with a power of 3.1 mW. **Figure 15a** and **b** displays the thermography images of the sample while being irradiated at time zero and 2 min later. The temperature of the sample increased from 24.7 to 31.0°C. This confirms that GNSs are able to absorb

Synthesizing GNS by seeding and growing a gold shell over silica spheres with GNPs showed to be an effective method to tune their absorption to the NIR. The SEM and TEM images show the evolution of the process, while the absorbance spectrum displays the GNS shifting over the NIR. Therefore, we obtained a simple technique of producing GNS that can be used for medical applications thanks to the bio-inert GNPs [3] and the widely studied cytotoxicity of the silica [5]. This method does not require long periods of time, when compared with previously published

We thank Consejo Nacional de Ciencia y Tecnologia (Conacyt) and Centro de Investigacion en Materiales Avanzados (CIMAV) for the financial support, Dr. Jose Guadalupe Murillo Ramirez for his help with the use of 852 nm wavelength laser, Dr. Pedro Piza for lending us the thermographic camera, Ing. Wilber Antunez Flores, and M.C. Karla Campos Venegas for helping us obtain the TEM and SEM

bigger than their size, exciting the electrons of the conducting band [2].

**4.6 Heat generation of GNS from light energy**

mechanisms, and does not need sophisticated equipment.

light from the NIR and convert it in heat.

**5. Conclusions**

**Figure 15.**

*laser for 2 min.*

**Acknowledgements**

**100**

images.

